1. Field of the Invention
Generally, the present invention relates to the field of europium compounds. More specifically, the present invention relates to a compound for uses of these compounds.
2. Description of the Related Art
Europium is a metal about as hard as lead and is quite ductile. It becomes a superconductor when it is simultaneously at both high pressure (80 GPa) and at low temperature (1.8 K). The occurrence of superconductivity is due to the applied pressure driving europium from a divalent (J=7/2) state into a trivalent (J=0) state. In the divalent state, the strong local magnetic moment is thought to play a role in suppressing the superconductivity and so through eliminating this local moment the opportunity for superconductivity arises.
Europium is a reactive rare earth element; it rapidly oxidizes in air (bulk oxidation of a centimeter-sized sample within several days) and resembles calcium in its reaction with water. Samples of the metal element in solid form, even when coated with a protective layer of mineral oil, are rarely shiny.
Divalent europium is a mild reducing agent, and under atmospheric conditions, it is the trivalent form that predominates. Under anaerobic, and particularly under geothermal conditions, the divalent form is sufficiently stable such that it tends to be incorporated into minerals of calcium and the other alkaline earths. This is the cause of the “negative europium anomaly” that depletes europium from being incorporated into the most usual light lanthanide minerals such as monazite, relative to the chondritic abundance. Bastnasite, another lanthanide mineral, tends to show less of a negative europium anomaly than monazite does, and hence is the major source of europium today. The accessible divalent state of europium has always made it one of the easiest lanthanides to extract and purify, even when present in low concentration, as it usually is.
The magnetic and optical properties of the divalent state of europium make this ion extremely attractive for use in materials, catalysis, luminescence, magnetic, and diagnostic-medical applications. A major hindrance to the use of Eu(II) in many of these applications is the extreme propensity of the ion to oxidize to Eu(III), especially in aqueous solution. Research efforts aimed at increasing the stability of aqueous Eu(II) have yielded moderate success: even the aqueous Eu(II) complex (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane europium(II), 1-Eu), previously reported to have the most positive oxidation potential, is not stable enough in aqueous solution for practical use.
It would therefore be useful to develop and generate Eu(II) complexes in aqueous solution.